Optical fibre cable core for submarine use

Claim 2

An optical fibre core for a submarine cable having a central longitudinal cable axis, the core comprising, as a longitudinal strength member of the core: (a) an elongated thermotropic plastics tube at least partly composed of a thermotropic liquid crystal polymer and extending linearly along the central longitudinal cable axis, said tube having a generally rectangular-section longitudinal central passage formed with a passage width, said tube having an outer surface of generally rectangular-section, said tube having a wall thickness of uniform cross-section and a thickness substantially smaller than its width; (b) a protective sheath encasing said tube; and (c) at least one optical fibre ribbon of generally rectangular-section and having major surfaces, said ribbon having a width which is slightly less than the width of the passage, said ribbon being housed loosely within said passage, said ribbon thereby being constrained to undulate in two dimensions in a longitudinal plane normal to said major surfaces.

Claim 3

A core as claimed in claim 1 wherein said ribbon is part of an integral stack of such ribbons.

Claim 4

A core as claimed in claim 1 wherein the tube is surrounded by at least on strain wire layer.

Claim 5

A core as claimed in claim 1 wherein said tube is encased in a protective sheath, said sheath having a material selected from the group containing thermosetting and thermoplastic polymer(s).

Claim 6

A submarine cable having a central longitudinal cable axis and an optical fibre core, the core comprising, as a longitudinal strength member of the core: (a) an elongated thermotropic plastics tube at least partly composed of a thermotropic liquid crystal polymer and extending linearly along the central longitudinal cable axis, said tube having a generally rectangular-section longitudinal central passage formed with a passage width, said tube having an outer surface of generally rectangular-section, said tube having a wall thickness of uniform cross-section and a thickness substantially smaller that its width; (b) at least one strain wire layer surrounding said tube; (c) a protective sheath encasing said tube and said strain wire layer; and (d) at least one optical fibre ribbon of generally rectangular-section and having major surfaces, said ribbon having a width which is slightly less than the width of the passage, said ribbon being housed loosely within said passage, said ribbon thereby being constrained to undulate in tow dimensions in a longitudinal plane normal to said major surfaces.

Claim 7

A submarine cable having a central longitudinal cable axis and an optical fibre core, the core comprising, as a longitudinal strength member of the core: (a) an elongated thermotropic plastics tube at least partly composed of a thermotropic liquid crystal polymer and extending linearly along the central longitudinal cable axis, said tube having a generally rectangular-section longitudinal central passage formed with a passage width, said tube having an outer surface of generally rectangular-section, said tube having a wall thickness of uniform cross-section and a thickness substantially smaller that its width; (b) at least one strain wire layer surrounding said tube; (c) a protective sheath encasing said tube and said strain wire layer; and (d) at least one optical fibre ribbon of generally rectangular-section and having major surfaces, said ribbon having a width which is slightly less than the width of the passage, said ribbon being housed loosely within said passage, said ribbon thereby being constrained to undulate in tow dimensions in a longitudinal plane normal to said major surfaces.